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From: pereira@sri-unix.UUCP
Newsgroups: net.sources
Subject: Prolog library: files.pl
Message-ID: <96@sri-unix.UUCP>
Date: Mon, 15-Aug-83 01:51:51 EDT
Article-I.D.: sri-unix.96
Posted: Mon Aug 15 01:51:51 1983
Date-Received: Thu, 11-Aug-83 13:36:29 EDT
Lines: 88

/* FILES.PL : Routines for playing with files

						UTILITY
						Lawrence
						Updated: 2 April 81
*/

	%%%  Compile this module
	%%%  FILES requires no other modules


  :- public check_exists/1,
	    file_exists/1,
	    open/1,
	    open/2,
	    close/2,
	    delete/1.


  :- mode check_exists(+),
	  file_exists(+),
	  open(+),
	  open(?,+),
	  close(+,+),
	  delete(+).




			% Check to see if a file exists and provide
			%  an error message if it doesn't

check_exists(File)
     :-	file_exists(File),
	!.

check_exists(File)
     :-	ttynl, display('! File: '), display(File),
	display(' does not exist.'), ttynl,
	fail.



			% Succeed if a file exists, otherwise fail

file_exists(File)
     :-	atom(File),
	seeing(Old),
	( nofileerrors  ;  fileerrors, fail ),
	see(File),
	fileerrors,
	seen,
	see(Old),
	!.



			% Open a file, checking that it exists

open(File)
     :-	check_exists(File),
	see(File).



			% Open a file and return current file

open(Old,File)
     :-	seeing(Old),
	open(File).



			% Close file and see old file again

close(File,Old)
     :-	close(File),
	see(Old).



			% Delete a file (note that rename requires that
			%  the file be open)

delete(File)
     :-	open(Old,File),
	rename(File,[]),
	see(Old).